Re: MN and the Principia

Brian D Harper (bharper@postbox.acs.ohio-state.edu)
Wed, 01 Apr 1998 17:20:03 -0500

At 10:32 AM 3/27/98 -0600, Paul Nelson wrote:

>
>Wayne R. Belcher wrote:
>
>>I was rectnly purusing the ASA archives and in a recent posting you stated
>>that Newton's _Principia_ does not speak of MN. I would disagree. Consider
>>the following quote from Book 3 (Rules of Reasoning and Philosophy):
>>"We are to admit no more causes of natural things than such as are both true
>>and sufficient to explain their appearance; therefore to the same natural
>>effects we must, as far as possible, assing the same causes."
>>This seems to be a pretty clear indication of MN to me.
>
>Not to me.
>
>Notice that Newton says "to the same natural effects we must...assign
>the same causes." The adjective "natural" occurs before "effects," but
>NOT before "causes" -- which is consistent with the rest of the _Principia_:
>
> This most beautiful system of the sun, planets, and comets,
> could only proceed from the counsel and dominion of an
> intelligent and powerful Being. And if the fixed stars are the
> centres of other like systems, these, being formed by the
> like wise counsel, must be all subject to the dominion of
> One; especially since the light of the fixed stars is of the
> same nature with the light of the sun, and from every system
> light passes into all other systems: and lest the systems of
> the fixed stars should, by their gravity, fall on each other, he
> hath placed those systems at immense distances from each
> other. (General Scholium)
>

Thanks for this quote from Newton. For those who don't have
a copy of Principia, you can find Mott's translation of the
General Scholium at:

http://www.kaiwan.com/~lucknow/horus/etexts/genlschl.html


Over the past few weeks I've been trying to develop Newton
as a role model for MN, so I was very interested to see
that Paul, whose views I always respect, disagrees so strongly
with this view of Newton.

Since MN seems to be used in different ways by different people,
I thought I'd mention my personal preference for the definition
given by Phil Johnson:

"the principle that science can study only the things that
are accessible to its instruments and techniques"

This, I believe, Newton would have endorsed without reservation.

Okay, first I will point out that the quote Paul gives comes
from the General Scholium (which Paul noted of course). According
to the Merriam-Webster dictionary (http://www.m-w.com/dictionary):

============================
Main Entry: schoŠliŠum
Pronunciation: 'skO-lE-&m
Function: noun
Inflected Form(s): plural schoŠlia /-lE-&/; or -liŠums
Etymology: New Latin, from Greek scholion comment, scholium,
from diminutive of scholE lecture
Date: 1535

1 : a marginal annotation or comment (as on the text of a
classic by an early grammarian)

2 : a remark or observation subjoined but not essential
to a demonstration or a train of reasoning
============================

Here I'm assuming that the second definition is appropriate.
I realize the potential danger of relying on a dictionary
definition, so if anyone has knowledge that scholium may
have meant something different in Principia, please let me
know.

Okay, my argument will be that this scholium contains Newton's
theological views which he recognized as being separate from
his scientific arguments. In order to make this clear, he
sets these views aside in a scholium.

Much better support for this view comes from the fact that
Newton does not even mention God in the first edition of
Principia. The General Scholium from which Paul quotes
was added 26 years later in the 2nd edition. Newton had
been severely criticized for not mentioning God in the
1st edition. Several authors have mentioned that, at that
time, not mentioning God was taken by many to be equivalent
to disavowing God. Unfortunately, many seem to have the
same view today :). In any event, it was Roger Cotes, editor
of the 2nd edition, who recommended the content of the
General Scholium:

"I think it will be proper [to] add something by which
your Book may be cleared from some prejudices which
have been industriously laid against it."
-- Roger Cotes in a letter to Newton

As the final prong of my argument, I'll give what may
be the most often quoted passage from Principia containing
the famous "hypotheses non fingo". This can be found
towards the end of the General Scholium:

==================================
But hitherto I have not been able to discover the cause
of those properties of gravity from phenomena, and I
frame no hypothesis; for whatever is not deduced from
the phenomena is to be called an hypothesis; and hypothesis,
whether metaphysical or physical, whether of occult
qualities or mechanical, have no place in experimental
philosophy. In this philosophy particular propositions
are inferred from the phenomena, and afterwards rendered
general by induction. Thus it was that the impenetrability,
the mobility, and the impulsive force of bodies, and the
laws of motion and of gravitation, were discovered. And
to us it is enough that gravity really does exist and act
according to the laws which we have explained, and abundantly
serves to account for all the motions of the celestial bodies
and of our sea.
-- Newton, from the General Scholium, Principia Book III
====================================

I think it's important to note here an error in translation
in the above. Koyre <Newtonian Studies> refers to this as
the worst kind of translation error, i.e. one where the
translator imposes their own interpretation. What Newton
wrote was "hypotheses non fingo" which means "I feign no
hypothesis" instead of Mott's "I frame no hypothesis".
Framing and feigning are obviously not the same thing.

Koyre also goes into some detail about what Newton meant
by hypothesis, and especially how this meaning changed
throughout Newton's career. In the above, the term is
used pejoratively, it refers to some unfounded gratuitous
assumption which cannot be deduced from the phenomena.

Further insight can be gained from what Newton wrote
to Richard Bentley:

========================================
That Gravity should be innate, inherent, and essential to
matter, so that one body may act upon another at a distance
through a vacuum, without the mediation of anything else,
by and through which their action and force may be conveyed
from one to another, is to me so great an absurdity that I
believe no man who has in philosophical matters a competent
faculty of thinking can ever fall into it. Gravity must be
caused by an agent acting constantly according to certain
laws; but whether this agent be material or immaterial I
have left to the consideration of my readers.
-- Newton, from his third letter to Richard Bentley
========================================

Note in particular "...left to the consideration of my readers"

Okay, so how can we reconcile these things with what Newton
wrote in the first part of the General Scholium, from which
Paul quoted?

"This most beautiful system of the sun, planets, and comets,
could only proceed from the counsel and dominion of an
intelligent and powerful Being." -- Newton

Did Newton really deduce this from the phenomena, or is
this rather a hypothesis which he is supposed never to
feign? IOW, does Newton contradict himself in the first
and second parts of the General Scholium?

I would argue instead that Newton added the above about
feigning hypotheses in order to emphasize that the preceding
comments represented his theological views which he wished
to remain distinct from his scientific arguments.

Brian Harper
Associate Professor
Applied Mechanics
The Ohio State University

"It is not certain that all is uncertain,
to the glory of skepticism." -- Pascal